The fictional actors are based on actors that appeared on The Expendables 3 (2014), which is similar to the fictional "The Indestructibles" and came out in the same year. Lance DeLorca is Antonio Banderas (he was born in Spain, was married to his one-time American co-star for decades before they got a divorce, and survived cancer, plus the scene of "Hard Kill" resembles the climatic scene in Banderas' action debut, Desperado (1995)); Brock Harmon is Sylvester Stallone (created a franchise of action movies starring aging action stars and made porn at the beginning of his career); Rolf Magnus is Dolph Lundgren (former Scandinavian bodybuilder rumored to be a genius) and Serafina is Ronda Rousey (female mixed martial arts champion with no previous movie experience that could be her co-stars' granddaughter).
One of the actors on the film set is introduced as Rolf, "card carrying member of Mensa". Dolph Lundgren (on whom this character is clearly based) is actually a member of Mensa.
The movie "The Indestructibles" is a play on the movie "The Expendables".
A subplot of the episode is Beckett packing up and moving out of her apartment, presumably to move into the loft with Castle. In "He's Dead, She's Dead (2010)", while investigating the death of an alleged psychic, Castle recounts a reading she once did for him about "a beautiful woman" who would one day move into his loft and stay with him forever. At the time, Castle believed it was referring to his mother, but in hindsight it could also refer to his new bride.